1. Field of the Invention
This invention relates to an automatic lock slider for a slide fastener, and more particularly to an automatic lock slider in which at least a slider body is formed by pressing and a locking pawl and its associated part are compactly accommodated and secured in a yoke so that smooth assembling can be achieved.
2. Description of the Related Art
In assembling this type of automatic lock slider, a pull tab, a generally C-shape resilient locking pawl and a yoke are attached to a slider body composed of upper and lower wings joined together at one ends by a connector (i.e. a diamond portion). Some parts sum as the slider body and the pull tab may be formed by pressing or die casting. Further, the locking pawl should by no means be limited to having a resiliency by itself and may have an associated spring as a separate member.
A machine for pressing slider bodies is currently known as disclosed in, for example, Japanese Patent Publication No. SHO 31-5628. An example of the slider body formed by pressing is disclosed in Japanese Utility Model Publications Nos. SHO 56-45447 and 58-3527. In the slider body disclosed in these Japanese Utility Model Publications, an upper wing has, in addition to an aperture through which one end of a locking pawl is to be inserted, a plurality of projections and recesses, which are formed by pressing, in order to position the pawl before the yoke is attached to the slider body and for stabilization of the pawl posture. In the meantime Japanese Utility Model Publications Nos. SHO 55-17846 and 58-3527 describe the concept of holding part of a locking pawl in a box-like yoke, which is formed by pressing, by clenching or pressing opposite side walls of the yoke.
However, regardless of whether or not it is integral with the spring, the locking pawl, as disclosed in the foregoing prior art references, is in the form of a metal strip having a width greater than the width essentially needed for the pawl. As long as the locking pawl has an adequate degree of strength to ensure engagement with and disengagement from coupling elements of the slide fastener in response to the movement of the pull tab, it is preferable to reduce the size of the locking pawl to a minimum since the locking pawl is mounted on the upper surface of the upper wing and the locking pawl is received in the box-like yoke.
Nevertheless, the conventional locking pawls have a large width in order to have one end of the pawl bifurcated and to prevent the pawl from falling sideways during assembling so that automatic assembling can be achieved. Further, the upper wing of the slider body has on its upper surface a plurality of projections and recesses to support the bifurcated end of the pawl to stabilize the posture of the pawl during assembling.
As a matter of course, these projections and recesses have to be prevented from being exposed to the slider surface and it is hence inevitable to cover them together with the locking pawl so that the yoke has necessarily a large width compared to the essentially needed size. This somehow influences on the appearance of the slider.
Further, if the slider body is formed by pressing, the problem in outside view would become more serious. In pressing process, mere bending and punching would not have caused any problem, however, pressing the slider body to provide the above-mentioned projections and recesses would cause plastic deformation around the pressed areas. Consequently in order to prevent any plastic deformation during the pressing, the slider body had to be firmly clamped around the areas to be pressed. As a result, traces due to the clamping would leave around the pressed areas. These traces are too large to be entirely covered by the yoke as the width of the yoke has a limit. So the traces partly come out on the slider surface to give the product an unsightly appearance.